Certain components of brakes have a usable life, following which they must be replaced.
Brake pads and brake shoes include friction material which progressively wears away as the brake is used. Electromechanical wear sensors are known which can determine the amount of friction material wear and provide an indication to an operator that the brake pads or shoes require replacement. EP0877872 shows a sensor which monitors the movement of a brake component which moves in proportion to brake pad wear. The sensor outputs an electrical signal indicative of an amount of brake pad wear. Such a system relies on the progressive movement of the internal brake mechanism.
Also certain components of brakes have a fatigue life. By way of explanation, it is known that certain components made from certain materials (for example steel) to which a load is repeatedly applied and then release can “fatigue” whereby fatigue cracks develop within the component. There comes a point when the fatigue cracks are sufficiently large that the component fails by breaking in two.
Certain components of brakes may have a fatigue life and as such must be replaced before fatigue failure occurs.
Thus there is a need to be able to determine if any usable life remains in a brake component so that it can be replaced.